Just messed it up in my head. Here is how I got it:

If I cancel before departure I will be charged $100 (is it per leg or total?)
Also if I need to change dates, right?
If I want to change return after departure I will not be charged exchange fee only the fare difference.

And since I started this thread already...
What is the minimum upgrade class for CX and where I can look up the upgrade availability.


Penalties

1 - PSGR P1 ADT RULES DISPLAY
FARE COMPONENT 1 ADT LAXHKG CX MGX180US PU 1 S
FCL: MGX180US TRF: 206 RULE: GTCS BK: M
PTC: ADT-ADULT FTC: XEX-REGULAR EXCURSION
PE.PENALTIES

CANCELLATIONS

ANY TIME
CHARGE USD 100.00 FOR CANCEL/NO-SHOW/REFUND.
WAIVED FOR UPGRADE TO HIGHER FARE/ILLNESS OR DEATH OF
PASSENGER OR FAMILY MEMBER.
NOTE -
ON TOTALY UNUSED TICKET. PARTIALLY REFUND IS NOT
PERMITTED.
---------------
THE CHARGE IS WAIVED IN CASE OF ILLNESS OF
PASSENGER OR TRAVELING COMPANION OR DEATH OF
>
PASSENGER/FAMILY MEMBER/TRAVELING COMPANION.
VALID MEDICAL/DEATH CERTIFICATE REQUIRED.
---------------
THE WAIVER FOR UPGRADE TO HIGHER FARE IS APPLIED
TO THE UPSELL ON THE ORIGINAL TICKET WITH SAME
TRAVEL DATE ONLY.

CHANGES

BEFORE DEPARTURE
CHARGE USD 100.00.
NOTE -
100.00 USD PLUS FARE DIFFERENCE IF ANY.
REROUTING IS NOT PERMITTED.

AFTER DEPARTURE
CHANGES PERMITTED.
NOTE -
NO PENALTY TO CHANGE RETURN DATE BUT COLLECT
FARE DIFFERENCE IF ANY.
IF TICKET NEEDS TO BE REISSUED. NO TICKET
>
REISSURANCE FEE.
-------
REROUTING NOT PERMITTED.

1 - PSGR P1 ADT RULES DISPLAY
FARE COMPONENT 2 ADT HKGLAX CX KGW180US PU 1 S
FCL: KGW180US TRF: 206 RULE: GTCS BK: K
PTC: ADT-ADULT FTC: XEX-REGULAR EXCURSION
PE.PENALTIES

CANCELLATIONS

ANY TIME
CHARGE USD 100.00 FOR CANCEL/NO-SHOW/REFUND.
WAIVED FOR UPGRADE TO HIGHER FARE/ILLNESS OR DEATH OF
PASSENGER OR FAMILY MEMBER.
NOTE -
ON TOTALY UNUSED TICKET. PARTIALLY REFUND IS NOT
PERMITTED.
---------------
THE CHARGE IS WAIVED IN CASE OF ILLNESS OF
PASSENGER OR TRAVELING COMPANION OR DEATH OF
>
PASSENGER/FAMILY MEMBER/TRAVELING COMPANION.
VALID MEDICAL/DEATH CERTIFICATE REQUIRED.
---------------
THE WAIVER FOR UPGRADE TO HIGHER FARE IS APPLIED
TO THE UPSELL ON THE ORIGINAL TICKET WITH SAME
TRAVEL DATE ONLY.

CHANGES

BEFORE DEPARTURE
CHARGE USD 100.00.
NOTE -
100.00 USD PLUS FARE DIFFERENCE IF ANY.
REROUTING IS NOT PERMITTED.

AFTER DEPARTURE
CHANGES PERMITTED.
NOTE -
NO PENALTY TO CHANGE RETURN DATE BUT COLLECT
FARE DIFFERENCE IF ANY.
IF TICKET NEEDS TO BE REISSUED. NO TICKET
>
REISSURANCE FEE.
-------
REROUTING NOT PERMITTED.

As I read it, cancellation before departure incurs a penalty of $100. Cancellation of the return after departure gets no refund.

Date changes (to either leg) after ticketing but before departure cost $100 in total for each instance on which you change anything on the ticket (changing both dates at the same time is still just $100). Date changes to the return leg are free after you have taken the outbound leg.

I guess they are trying to give you a ticket which is good to cope with unexpected events while you are away, but not one which you can just buy and keep changing the date on before you start your trip.

YBHK are upgradeable with AsiaMiles. M is not. The CathayPacific site has a booking engine for AsiaMiles upgrades.